Technical Field
This disclosure relates generally to drilling tools, and in particular to a tool that may be configured in a reverse circulation exploration drilling system to guide the drilling operation toward the desired underground target.
State of the Art
Drilling is used around the globe as a means for accessing oil, water, geothermal and mineral resources within the Earth and gathering the resources therefrom. For example, water wells are traditionally formed through conventional drilling techniques, where wells are drilled vertically from the surface. Mineral exploration and mine development includes drilling to locate the minerals to be mined and using the extracted information by drilling to mine proven resources. Other drilling techniques, such as directional drilling are used to access underground locations in environmentally sensitive areas, so as to not have an environmental impact on the surface. Surface reverse circulation drilling is also utilized in underground mine rescue situations.
Yet, regardless of the type of drilling method utilized or the purpose for which the drilling is commenced, accuracy of the drilling system is paramount. Without accurately drilling and intercepting the intended target within the ground, the drilling operation will have expended significant sums of money to drill one or more holes without positive result. Generally by contractual agreement the drilling contractor is responsible for controlling deviation to reach the intended target within the ground.
Thus, prior to even beginning to drill, geologists take great care to attempt to pinpoint, or at least generally locate, the mineral resource to be drilled. Geologists map surface features that might indicate mineral resources under the ground. Geologists look for ore deposits using geophysical surveys. Geologists also use seismic surveys to map the location of petroleum resources within the earth. Seismic surveys utilize seismic waves that are sent down into the ground. These waves bounce off various features in the Earth and return to the surface at varying speeds, which the geologists may use to analyze and categorize what the ground may look like under the surface. In other words, geologists may get a picture of the composition of the ground at that particular location.
If these pre-drilling studies are positive, then it might justify test drilling, wherein one or more test wells are drilled in an attempt to evaluate the natural resources from the intended drill target for verification. Yet, even at this stage, geologists can come up with disappointing results if the drilling system is not able to accurately reach and access the predetermined underground target that the pre-drilling study has indicated is present.
Reverse circulation (RC) drilling is an example of type of drilling method that may be utilized as an exploratory drilling technique to reach predetermined locations (targets) under the ground and intercept mineral resources that may or may not exist. “Angle” drilling may be utilized with RC drilling, such that the drill string of the RC drilling system is angled from the vertical a certain number of degrees and enters the ground at this predetermined angle. Thereafter, whether the drill string accurately reaches the predetermined target under the ground is entirely up to the drill system components and the drill system operators.
In view of these difficulties, it is paramount that the drilling technique and the drilling system to be precise enough to locate and reach the exact location of the mineral resources determined by pre-drill study. For example, if the drill hole starts out at the surface in the direction of the mineral resource deep within the Earth and the drilling system cannot maintain course to the intended target of the mineral resource, then by the time the drilling system reaches the depth where the mineral resource is estimated, the drilling system may actually have deviated off target and miss the mineral target entirely. For example, the Chilean mine rescue in 2010 utilized 10 reverse circulation drilling rigs and took two weeks to intercept a target (i.e., the trapped miners) due to the problems associated with deviation of the drill holes.
Accordingly, there is a need in the drilling industry for tools that can be utilized by drill system operators to create an accurate drilling system that can drill an accurate enough hole in the Earth to reach a predetermined location within the depths of the Earth.